A symposium on "Epithelial-Mesenchymal Interactions in Development" has been approved by the American Society of Zoologists Divisional Program Officers. The symposium will be held at the 1981 Dallas Meeting of the ASZ. That epithelial-mesenchymal interactions or communications between embryonic tissues of different developmental orgins play a major role in organogenesis has been known for over 50 years. A comprehensive symposium (18th Hahnemann Symposium) on epithelial-mesenchymal interactons was held over 20 years ago at which time the intent was to determine the current status of the knowledge in the field and to evaluate the concepts of embryonic "induction." Although the mechanisms by which these tissue interactions occur still remain obscure, new concepts are emerging, with considerable attention being given to the roles of instructive vs permissive epithelial-mesenchymal interactions. It is the intent of this symposium to bring together those researchers interested in and working on mechanisms of tissue interactions. The various participants selected for this symposium are using novel systems and approaches to define the mechanisms involved in these interactions. The symposium will be published in the American Zoologist or as a book by a private publishing company.